Exhaust gas recirculation control by exhaust flow

ABSTRACT

An exhaust gas recirculation system for an internal combustion engine of the kind having an exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake includes valve means in the recycle conduit which are positioned in response to exhaust gas flow in the exhaust outlet.

United States Patent Walker Nov. 25, 1975 [54] EXHAUST GAS RECIRCULATION 3,507,260 4/1970 Walker 123/119 A CONTROL BY EXHAUST FLOW 3,664,313 5/1972 Walker 3,783,848 l/1974 Ranft etal. l23/ll9 A [76] Inventor: Brooks Walker, 1280 Columbus San Franclsco Cahf' 94133 Primary Examinerwendell E. Burns 22 Filed; 1, 1974 Attorney, Agent, or Firm-Owen, Wickersham&

Erickson [21] Appl. No.: 438,545

[57] ABSTRACT An exhaust gas recirculation System for an internal [58] Fieid 60/292 combustion engine of the kind having an exhaust gas recycle conduit for recycling a part of the exhaust [56] References Cited gases from the exhaust outlet back to the fuel-air intake includes valve means in the recycle conduit UNITED STATES PATENTS which are positioned in response to exhaust gas flow 2,700,967 2/1955 Maker l23/l l9 A in the exhaust outlet, 7 7 3,116,725 1/1964 Hadley.. 123/119 A 0 3,234,924 2/1966 May 60/292 30 Clams, 4 Drawing Flgures l4 IO TO ENGINE FUEL- AIR FROM ENGINE EXHAUST OUTLET POWER VALVE STORAGE INTAKE I SUCTION m i S INTAKE MANIFOLD U.S. Patent Nov. 25, 1975 Sheet2 of2 3,921,611

TO ENGINE FUEL-AIR INTAKE EXHAUST GAS20 l RECYCLE FLOW 50 66 PL, 24 45 I l\ TI ,5;

3]. b u W l k D 6 I I I7 f r 29 52 56 WIDE OPEN THROTTLE r" AT HIGH ENGINE SPEED WIDE OPEN THROTTLE. AT LOW ENGINE SPEED STARTING FIG 3 TO ENGINE FUEL-AIR INTAKE FROM 2 ENGINE EXHAUST OUTLET THROTTLE CRUISE EXHAUST GAS RECIRCULATION CONTROL BY EXHAUST FLOW BACKGROUND OF THE INVENTION This invention relates to an exhaust gas recirculation system for an internal combustion engine. It relates particularly to a recirculation system which recycles exhaust gases into the induction system for the primary purpose of reducing the oxides of nitrogen emitted from the exhaust.

The amount of nitrogen oxides emitted from an internal combustion engine is a function of combustion temperature. Relatively high combustion temperatures, such as occur during engine operation at partially open throttle at level cruise and at relatively high speeds, produce large amounts of nitrogen oxide emissions.

Such emissions are not critical during idling because the rate of fuel combustion is low enough that the combustion temperatures are relatively low.

The engine combustion temperatures normally increase with engine load and with the rate of acceleration at any speed.

However, engine operation at wide open throttle normally results in enough fuel enrichment by the power valve that the combustion temperatures are lowered enough to produce only acceptable amounts of nitrogen oxide emissions.

Recycling 5 to 25 percent of the total exhaust gases through the engine (depending on load and power demand) will usually reduce combustion temperatures to levels that do not produce unacceptable amounts of nitrogen oxide emissions. For example, recycling about fifteen percent of the total exhaust gases during partially open throttle will usually produce the desired result.

SUMMARY OF THE INVENTION It is a general object of the present invention to control the flow of exhaust gas recirculation (through an exhaust gas recycle conduit of the kind described) in a way that produces the desired reduction of nitrogen oxide emissions.

It is a primary object of the presentinvention to control the exhaust gas recirculation during engine operation in direct response to exhaust gas flow through the exhaust outlet of the engine.

The present invention incorporates valve means in the recycle conduit for regulating the flow of recycled exhaust gas through the recycle conduit and control means responsive to the exhaust gas flow in the exhaust outlet for positioning the recycle valve means.

The valve means include a valve seat and a movable valve element which is contoured to restrict to a minimum or to block all flow through the recycle conduit in a first (idle) position at one end of the travel of the valve element and also to restrict to a minimum or to block all flow through the recycle conduit in a second (wide open throttle) position at the other end of the travel of'the valve element.

The valve element is tapered to provide a flow area which varies with movement of the valve element between the first (idle) and second (wide open throttle) positions. This taper, in combination with the control means responsive to exhaust gas flow in the exhaust outlet, maintains an amount of exhaust gas recirculation flow which is generally-in relation to'the engine speed. The taper permits greater amounts of exhaust 2 gas recirculation flow at higher engine speeds and at increased engine loads and increased exhaust flow to the exhaust pipe outlet.

My U.S. Pat. No. 3,507,260. issued Apr. 2], 1970 and entitled Exhaust Recirculation Control for an Engine," shows in FIGS. 2 and 3 an exhaust recycle valve having a contour somewhat similar to that of the present invention. This patent, however, does not disclose control means responsive to exhaust gas flow in the exhaust outlet of the engine for positioning the recycle valve.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view, partly broken away in cross-section, showing an exhaust gas recirculation system constructed in accordance with one embodiment of the present invention;

FIG. 2 is an end elevation view in cross-section taken along the line and in the direction indicated by the arrows 2-2 in FIG. 1;

FIG. 3 is a side elevation view in cross-section of an exhaust gas recirculation system constructed in accordance with another embodiment of the present invention. FIG. 3 shows a spring link in the connection between the flapper valve and the exhaust gas recycle control valve which permits the flapper valve to go to a more open position at wide open throttle at high speeds than at wide open throttle at low speeds while the exhaust gas recycle control valve remains fixed in a closed position;

FIG. 4 is a side elevation view in cross-section of an exhaust gas recirculation system constructed in accordance with a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In all Figures corresponding parts are indicated by the same reference numerals.

An exhaust gas recirculation system constructed in accordance with one embodiment of the present invention is indicated generally by the numeral 10 in FIG. I.

The exhaust gas recirculation system is part of an internal combustion engine (not shown in the drawings). The engine includes an exhaust pipe 12 which, as illustrated in FIG. 1, may have an angled extension 12a.

The system 10 includes an exhaust gas recycle conduit 14 connected to the engine exhaust outlet 12 at one end by a fitting indicated generally by the reference numeral 16. The conduit 14 is preferably a high temperature hose which can be made of Teflon or corrugated flex tubing such as commercially available copper-brass constructions or other suitable material. The recycle conduit includes a section 14a connected to the engine induction apparatus (not shown). Thus, in the form illustrated in FIG. 1 one end of the conduit section 14a is slipped over a fitting 18 and the other end is connected to the engine intake manifold or to the carburetor below the throttle valve.

As illustrated in the phantom outline in FIG. 1, the length of the recycle conduit 14 can be shortened by a connection 14a to the pipe 12a in place of the connection through the fitting 16 to the pipe 12 as illustrated.

In accordance with the present invention, valve means 20 are connected in the recycle conduit 14 for controlling the amount of flow of the exhaust gases through the recycle conduit.

The valve means comprise a housing 22 having an internal valve seat 24.

The valve means 20 also include a valve element 26 which is movable, by an actuating stem or rod 28, with respect to the fixed valve seat 24.

The valve element 26 is positioned in response tothe exhaust gas flow by a flapper valve 30 (mounted in the pipe 12 for swinging movement about one edge by a pivot 32) and a connecting mechanism which includes a link 36 and a bar 34. The bar is on the outside of pipes 12 and 12a and is fixed for rotation with the flapper 30.

The bar 34 has a series of holes 38. One end of the link 36 is connected in a selected one of the holes 38 to produce the desired axial movement of the valve element 26. The other end of the link 36 is connected to the link 28'. This connection may include a pin joint 40 to provide the required articulation of the mechanism as illustrated.

Thus, as the exhaust flow in the pipe 12 increases on increasing engine speed or power the flapper valve 30 is pushed downward (as viewed in FIG. 1) at increasing angular inclinations about the pivot 32 (as indicated by the legends idle", cruise, and wide open throttle" in FIG. 1).

The flapper valve and pivot 32 thus provide control means responsive to the exhaust gas flow for positioning the valve means 20, and the pivot pin and links 36 and 28 provide connecting means for connecting the flapper valve 32 to the movable valve element 26. While the valve 30 is illustrated as a flapper valve, other valve constructions, such as a poppet valve with sufficient area around the valve to allow full exhaust flow, could be used.

In FIG. 1 the flapper valve 30 is shown in a solid line position in which the flapper valve is held slightly open for easy starting of the engine without excessive exhaust gas back pressure. This position also permits relatively unrestricted flow of the engine exhaust gases. As,

will be described in more detail below the flapper valve 30is either moved to the solid line position during starting by a solenoid 70 or is prevented from going to a more closed position by an alternate, adjustable stop 80.

In this solid line position of the flapper valve 30, the bar 34 is also in the solid line position illustrated. The bar 34 is biasedtoward the solid line position byv a spring 42. The spring is seated at one end against a spring seat 44 fixed to a guide tube 45 which is in turn fixed to the housing 22. The other end is seated against a part 46 attached to the link 28 by a shoulder or collar 28a. The part 46 is slidable within the tube 45. The stem 28 slides within a central opening in the fixed spring seat 44. The housing 22 is detachably mounted on the pipe 12a by a support 50 and one or more screws 52.

As shown in FIG. 2 the fitting 16 can be installed by a relatively simple spring clip. An opening 52 is formed in the thin sidewall of the pipe 12 and is preferably formed from the inside out so as to have slightly outturned edges 52a as illustrated. A seal element, such as a high temperature O-ring 54, is positioned around the upturned edge 52 as illustrated, and a tube 56 having a radially extending shoulder or flare 58 is placed in the opening 52. A spring clamp 60 having an opening 57 is slipped over the tube 56 and around the pipe 12. The ends of the clamp 60 are pulled together by a bolt 62 and nut 64. This pulls the flange 58 down in a gas tight seal against the edge 52a and the seal 54. One end of 4 the conduit 14 is slipped over the other end of the conduit 14 is slippedover a corresponding tubular part 66 projecting outwardly from the housing 22. The tube 56 can be welded or brazed to the exhaust pipe 12 or secured in any other suitable manner, but for retrofitthe method shown in FIG. 2 may be easy.

Though not illustrated in detail in FIG. 1, the connection for the alternate tube 14a to the pipe 12a can be made in the same way as illustrated in FIG. 2 for the fit ting 16. I

Since the pivot 32 is exposed to relatively high exhaust gas temperatures and is also subjected to the buildup of carbon and corrosion from the exhaust A gases, the shaft to which the flapper valve 30 is at:

tached is preferably made of stainless steel (about Vs in diameter) and is preferably mounted in carbon or brass bushings to reduce the chance of corrosion. Since the flapper valve 30 is spring biased by the spring 42 and because the flapper valve 30 moves with changes in eX- I haust volume and even with some of the pulses between the cylinder exhausts, the flapper valve 30 moves more or less continuously and thus tends to prevent sticking As noted above, in the solid line position of the flapper valve 30, the flapper valve 30 is held open for easy starting, and the left end of valve element 26 (as viewed in FIG. 1) is engaged with the valve seat 24 to block I line 76. The flapper valve 30 will then be rotated to ap 1 proximately the idle position indicated.

It should be noted that the bar 34, links 38 and 28, and housing 22 including spring guide tube 45, are mounted entirely on the outside of pipes 12 and 12a so that all this mechanism is freely movable to the various positions produced by deflection of the flapper valve As illustrated by the phantom outline in FIG. 1, an

adjustable stop 80 may be associated with the bar34 for engaging the left edge (as viewed in FIG. 1) of the bar to limit the extent to which the flappervalve 30 can be moved to a closed position by the spring 42. In this form of the invention, a nut 82 is fixed in position on the outside of the pipe 12a and the screw 80 is rotated within the nut 82 to the position desired. When the adjustable stop 80 is used, the solenoid 70 is not required for connection with the engine starter circuit.

The valve element 26 has an enlarged end 27 at one end (at the left end as viewed in FIG. 1), a tapered central portion 29 (which diminishes in diameter from left to right as viewed in FIG. 1) and a radially extending shoulder or flange 31 at the other end (the right end as viewed in FIG. 1). The shoulder 31 has a valve seat engaging face 310 which may be slightly tapered as illustrated and which engages the valve seat 24 in flow blocking or restricting contact when the flapper valve 30 is rotated to the wide open throttle position indicated in FIG. 1. The shape of the valve between the two ends can be tailored to the desired EGR opening for each position of the exhaust flapper valve 30 for th best nitrous oxide control.

In the operation of the exhaust gas recirculation system illustrated in FIG. 1 the flapper valve 30 is held slightly open for starting, either by the solenoid or tube 56, and the by the adjustable stop 80. In this position of the flapper valve 30 the enlarged end 27 of the valve element 26 is positioned with respect to the valve seat 24 so as either to completely block flow of recycled gases through the conduit 14 or to permit only a very minimum amount of such flow since exhaust gas recirculation is not needed to reduce the relatively low combustion temperatures in the engine which are produced at idle.

As the engine speed or power increases the flapper valve 30 is deflected progessively downward by the increasing exhaust gas flow, and this moves the valve element 26 to the left (as viewed in FIG. 1) to position the tapered central section 29 in line with the bore 24a in the valve seat 24. The angle or contour of taper of the central part 29 is such as to maintain a relatively constant relationship between the percent of exhaust gas recycled through the conduit 14 and the total amount of exhaust gases flowing through the exhaust pipe 12. That is, as the flow of engine exhaust gases in the pipe 12 increases with engine speed, the size of the opening in the valve means 24 also increase right up to the time that the shoulder 31 engages the valve seat 24 to block flow at wide open throttle. This continuously increasing size of the opening in the valve means is important since the intake suction decreases significantly at engine operating conditions approaching wide open throttle, and the larger opening size is therefore required to insure that the increased recycle gas flow is obtained. The exhaust back pressure also increases due to muffler back pressure as the exhaust flow increases which adds to the recycle flow as the intake suction decreases.

As noted above, recycled exhaust gases are not required to hold down combustion temperatures at wide open throttle since the power valve of the carburetor sufficiently enriches the fuel air mixture under such conditions of operation to lower combustion temperatures to levels at which excessive amounts of nitrous oxide emissions are not produced.

In some cases a delay system is associated with the power valve to delay operation of the power valve for a fixed period of time (e.g. a delay in the range of 5-10 seconds) after the engine throttle is moved to a wide open throttle position. Such -a delay system is shown in my U.S. Pat. No. 3,664,313. This delay system is used to prevent operation of the power valve for relatively short periods of wide open throttle operation (such as going up a short hill or short acceleration in city driving) to prevent producing certain air pollutants because of the enriched fuel-air mixture produced by the power valve. That is, the enrichment produced by the power valve, while it decreases combustion temperatures and thereby reduces nitrous oxide emissions, can produce other undesirable exhaust emissions. A short delay in operation of the power valve to prevent operation of the power valve during brief periods in city driving (while permitting operation of the power valve for prolonged upgrades in out of the city driving to prevent overheating of valves etc. at and near wide open throttle continued operation might occur with a lean mixture without the power valve) may therefore be desired.

When the power valve is on, the enrichment lowers combustion temperatures to a level where exhaust gas recycling is not needed to prevent formation of excessive nitrous oxide emissions. When the power valve operation is delayed at wide open throttle, the exhaust gas recycled flow should be continued (until the power valve does come on) to maintain lower combustion temperatures.

The present invention provides for this mode of operation.

In FIG. 1 a power valve delay mechanism is indicated generally by the reference numeral 100. This mechanism is basically the same as that shown in my U.S. Pat. No. 3,664,313 issued May 23, 1972 and entitled Carburetor" and will therefore not be described in detail in this application.

A line 102 extends from the engine induction system to a storage chamber and a line 104 interconnects the power valve with a delay mechanism and the storage chamber in the manner described in my above noted U.S. Pat. No. 3,664,313.

A suction operated motor 105 has a spring 106 calibrated to hold the diaphragm 107 against the housing fully to the right (as viewed in.FIG. 1) whenever the suction on the spring side of the diaphragm is at or very near atmospheric. However, at greater suctions the action of the atmospheric pressure on the right side of the diaphragm 107 compresses the spring and moves the diaphragm washers 109 against a stop 11]. This positions a stem 108 so that the stem 108 holds the lever 34 away from the wide open throttle position of the valve 30. This in turn insures that the valve shoulder 31a is not against the seat 24 to allow a sizeable opening for exhaust gas recirculation flow until the delay reduces the suction in the line 104a to allow the power valve 100 to open and the stem 108 to be retracted.

When the stem 108 is retracted, the valve element is then permitted to move to a position in which the exhaust gas recirculation flow is blocked or greatly restricted by the valve shoulder 31a.

Thus, in the operation of the combined power valve delay mechanism 100 and the exhaust gas recirculation system 10 shown in FIG. 1, when the throttle is moved toward wide open the flapper valve 30 first rotates the bar 34 about the pivot 32 to the phantom position as limited by the stem 108. In this position of the bar 34 the shoulder 31 is slightly spaced from the valve seat 24, the maximum opening through the valve means 20 is therefore produced. The bar 34 and the valve element 29 are held in this position for the period of time (determined by the delay mechanism 100) that the operation of the power valve is delayed. When the suction in the lines 104 and 104a drops to a level that permits the power valve to come on, the motor 105 simultaneously retracts the stem 108 to let the bar 34 pivot far enough to shut off or to greatly restrict the flow of recirculated exhaust gas through the valve 20 and the conduit 14.

An exhaust gas recirculation system constructed in accordance with a second embodiment of the present invention is indicated generally by the reference numeral 11 in FIG. 3. The FIG. 3 embodiment incorporates a spring link in the connection between the flapper valve 30 and the valve element 26 for permitting the flapper valve to swing to a more open position in the exhaust pipe during engine operation at wide open throttle at high engine speeds than during engine operation at wide open throttle at low engine speeds without affecting the engagement of the valve element 26 with the valve seat 24 at such wide open throttle conditions.

As illustrated in FIG. 3 the spring may comprise a generally S-shaped section 36a in the link 36 to provide the required flexibility and lengthening of the link as the flapper valve 30 is rotated further upward (as viewed in FIG. 3) about the pivot 32 from wide open throttle at low engine speeds such as miles per hour to wide open throttle at high engine speeds such as 60 miles per hour to accommodate the increased exhaust gas flow through the pipe 12 at the higher engine speeds. In both conditions of operation the connection of the flapper valve plate to the pin 32a and the bar 34 rotates the pin 320 within the bushing 36b to an angular position of the bar 34 which engages the end 31 with the valve seat 24. As the flapper valve 30 rotates further at higher engine speeds, the spring 36a permits the link 36 to, in effect, extend or elongate to permit increased movement of the bar 34..

Since in the FIG. 3 embodiment the connection of the flapper valve 30 in the pipe 12 is reversed with respect to that in the FIG. 1 embodiment, the connection of the valve element 26 to the stem 28 isalso reversed.

The seating of the spring 42 is also somewhat differ ent in FIG. 3 in that the fixed spring seat 44 is at the right end of the tube 45 and the spring seat 46 carried on the stem 28 is near the left end of the tube 45.

A guide block 47 is positioned at the extreme left end of the tube 45 to provide a guide at that location for the stem 28. This block 47 can also be used as a stop (as shown in FIG. 4) for limiting closing movement of the flapper valve 30. However, an adjustable stop 80 may be preferred. As illustrated in FIG. 3, the adjustable stop may include a locking nut 82a for holding the stop in an adjusted position.

The operation of the FIG. 3 embodiment is basically the same as that described above with reference to the FIG. 1 embodiment and will therefore not be repeated.

A third embodiment of an exhaust gas recirculation system constructed in accordance with the present invention is indicated generally by the reference numeral 13 in FIG. 4. This FIG. 4 embodiment is basically like that shown in FIG. 3 with the exception of the pivot means for the flapper valve 30 and the connection between the flapper valve 30 and the stem 28.

In the FIG. 4 embodiment the pin 32a and bushing 32b of the FIGS. 1 and 3 forms are replaced by a flexible hinge 110 which is welded or otherwise attached at its lower end to the flapper valve 30 and which is attached to the exhaust pipe 12 at its upper end as by screws 112. This flexible hinge construction eliminates problems of corrosion and sticking due to carbon deposits that might develop with pin and bushing arrangements after long periods of time. The hinge member of 110 is preferably made of light gauge, corrosion resistant, spring steel to permit free swinging movement of the flapper valve 30 about the edge connected to the screws 112.

In the FIG. 4 embodiment the exhaust pipe 12 is formed with an upper opening 114 for the installation of the flapper valve 30 and hinge 110, and this opening is then closed by a cover 116. The cover 116 is held in place by the screws 112 and by a second set of screws 118.

The stem 28 .is connected to the flapper valve 30 by a roller 120 mounted for rotation on the lowermost end of the stem 28. The roller 120 is held in engagement with the back surface of the flapper valve 30 (the surface not directly exposed to the exhaust gas flow) by a retainer guide 122. The roller 120 is thus free to roll along the back surface of the flapper valve 30 as the flapper valve 30 swings up and down with changes in exhaust gas flow to transmit this motion of theflapper,

The operation of the FIG. 4 embodiment is basically like that described above with reference to FIGS. 1 and 2 and will therefore not be repeated.

The various embodiments of the present invention thus provide an exhaust gas recirculation system which regulates the exhaust gas recycle flow in response to the amount of exhaust gas flow from the engine. The system of the present invention provides for a'very re-' stricted or complete blocking of the recycle flow atengine idle. The system also provides for blocking of the recycle flow during engine operation at wideopen throttle with the power valve on. The present invention provides for substantially complete restriction or com-, plete blocking of exhaust gas flow at idle while permit ting relatively unrestricted flow through the engine ex-.

haust outlet for easy starting, and the present invention also can be coordinated with delayed operation of the power valve to maintain flow of recycled exhaust gas at, wide open throttle until the power valve comes on.

To those skilled in the art to which this invention relates, many changes in construction and widelydiffe ring embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

1. An exhaust gas recirculation system for an internal I combustion engine of a kind having an exhaust outlet, a fuel-air intake and an exhaust gas recycle conduit for.

recycling a part of the exhaust gases from the exhaust;

outlet back to the fuel-air intake, said system'comprising,

valve means in the recycle conduit for regulating the amount of flow of said recycled exhaust gases through the recycle conduit, and

control means responsive to the exhaust gas flow in said exhaust outlet for positioning said valve means said control means including a valve in the-exhaust outlet mounted for movement in response to changes in exhaust gas flow and operatively con-,

nected to said valve means in the recycle conduit for controlling the exhaust gas recirculation through many changes inengine operating condi- I tions. 2. The invention defined in claim 1 wherein the valve means are contoured to restrict the flow of exhaust gas through the conduit to a first minimum in a first position of the valve means, to restrict the flow to a second minimum in a second position of the valve means,and to permit greater flow than said minimums in all positions of the valve means between said first and second positions. I

3. The invention defined in claim 2 wherein the valve means include a fixed valve seat and a movablervalve element.

4. The invention defined in claim 3 wherein the valve means include an annular seat and the valve element has an elongated body movable in the annular seat and 9 has a flange which engagesthe annular seat in the first position.

5. The invention defined in claim 4 wherein the body is tapered and has a small diameter immediately adjacent the flange and a large diameter at an end of the body away from the shoulder.

6. The invention defined in claim 5 wherein the taper is contoured to maintain a desired relationship of exhaust gas recirculation flow to movement of said control means.

7. The invention defined in claim 2 wherein the control means are effective to position the valve means in the first position at engine idle.

8. The invention defined in claim 2 wherein the control means are effective to position the valve means in the second position at wide open throttle.

9. The invention defined in claim 2 wherein the control means are effective to position the valve means in positions between the first and second positions at conditions of engine operation between idle and wide open throttle.

10. The invention defined in claim 1 wherein the valve includes a portion large enough to extend across substantially the entire cross-sectional area of the flow area through the exhaust outlet and including start-up means for preventing the valve from moving to a position in which the valve completely blocks flow through the exhaust outlet during engine start-up.

11. An exhaust gas recirculation system for an internal combustion engine of a kind having an exhaust outlet, a fuel-air intake and an exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said system comprising,

valve means in the recycle conduit for regulating the the amount of flow of said recycled exhaust gases through the recycle conduit, and

control means responsive to the exhaust gas flow in said exhaust outlet for positioning said valve means and wherein the control means include a flapper valve which extends across at least a substantial part of the exhaust outlet so as to be subjected on one face to a force which is dependent upon the exhaust gas flow and which force is in general relation to engine speed and power between idle and wide open throttle, pivot means supporting the flapper valve for pivoting movement about a pivot substantially away from the center towards one edge of the flapper valve, and connecting means for transmitting pivoting movement of the flapper valve to said valve means in the recycle conduit.

12. The invention defined in claim 11 wherein the connecting means include an articulated connection.

13. The invention defined in claim 12 wherein the connecting means include biasing means for moving the valve means to a first position in which the valve means greatly restrict or block all flow through the recycle conduit at exhaust flows through said exhaust outlet corresponding to idle operation of the engine.

14. The invention defined in claim 13 wherein the valve means are contoured to greatly restrict or block all flow through the recycle conduit in a second position of the valve means at exhaust gas flows corresponding to engine operation at wide open throttle.

15. The invention defined in claim 11 wherein the pivot means include a flexible hinge member.

16. The invention defined in claim 11 wherein the pivot meansinclude a pivot pin and bushing.

17. The invention defined in claim 16 including flexible means in the connecting means for permitting the flapper valve to swing further about the pivot means at exhaust gas flows at wide open throttle at high speeds than at wideopen throttle at low speeds without changing the valve means from said second, flow blocking position.

18. The invention defined in claim 11 wherein the flapper valve is large enough to extend across substantially the entire cross-sectional area of the exhaust outlet and including start-up. means for preventing the flapper valve from swinging about the pivot to a position in which the flapper valve completely blocks flow through the exhaust outlet during engine start-up.

19. The invention defined in claim 18 wherein the start-up means include an adjustable stop.

20. The invention defined in claim 18 wherein the start-up means include means actuated in response to starting of the engine.

21. The invention defined in claim 11 wherein the connecting means include a roller which engages one surface of the flapper valve and which is movable along said surface with changes of angular position of the flapper valve about the pivot means.

22. The invention'defined in claim 2 wherein the engine includes a power valve for enriching the fuel-air ratio in the intake for acceleration at or near wide open throttle and including coordinating means for insuring that the valve means are in said second recycle flow blocking or restricting position during enrichment of the fuel-air ratio by said power valve.

23. The invention defined in claim 22 including delay means for delaying the opening of the power valve for a preselected period of time after the throttle is opened to or near wide open position.

24. An exhaust gas recirculation system for an inter. nal combustion engine ofa kind having an exhaust outlet, a fuel-air intake and an exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said system comprising,

valve means in the recycle conduit for regulating the amount of flow of said recycled exhaust gases through the recycle conduit, and

control means responsive to the exhaust gas flow in said exhaust outlet for positioning said valve means and wherein the valve means are contoured to restrict the flow of exhaust gas through the conduit to a first minimum in a first position of the valve means, to restrict the flow to a second minimum in a second position of the valve means, and to permit greater flow than said minimums in allpositions of the valve means between said first and second positions and wherein the engine includes a power valve for enriching the fuel-air ratio in the intake for acceleration at or near wide open throttle and including coordinating means for insuring that the valve means are in said second recycle flow blocking or restricting position during enrichment of the fuel-air ratio by said power valve and including delay means for delaying the opening of the power valve for a preselected period of time after the throttle is opened to or near wide open position and 1 1 including stop means movable to a first position in which the stop means prevent movement of the recycle valve means to the flow blocking or restricting position at or near wide open throttle.

25. The invention defined in claim 24 wherein the coordinating means move the stop means to a second position simultaneous with opening of the power valve to permit the valve means in the recycle conduit to move to the flow blocking or restricting position simultaneous with the opening of the power valve.

26. A method of controlling exhaust gas circulation through an exhaust gas recycle conduit in an internal combustion engine of the kind having an exhaust outlet, a fuel-air intake and said exhaust gas recycle conduit for recycling a partof the exhaust gases from the exhaust outlet back to the fuel-air intake, said method comprising, restricting exhaust gasrecirculation in said recycle conduit to a first minimum at idle, restricting exhaust gas recirculation in said recycle conduit to a second minimum at wide open throttle and controlling the amount of exhaust gas recirculation between idle and wide open throttle in response to exhaust gas flow in the exhaust outlet and including mounting a control valve in the exhaust outlet for movement in response to changes in exhaust gas flow, mounting a recycle valve in the recycle conduit and operatively connecting the control valve to the recycle valve.

27. The invention defined in claim 26 including mounting a flapper valve in the exhaust outlet for pivoting movement about one edge of the flapper valve to cause the swinging movement of the flapper valve about the pivot to be dependent upon the exhaust gas flow.

28. A method of controlling exhaust gas circulation through an exhaust gas recycle conduit in an internal combustion engine of the kind having an exhaust outlet, a fuel-air intake and said exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said method comprising, restricting exhaust gas recirculation in said recycle conduit to a first minimum at idle, restricting exhaust gas recirculation in said recycle conduit to a second minimum at wide open throttle and controlling the amount of exhaust gas recirculation between idle and wide open throttle in response to exhaust gas flow I in the exhaust outlet and-including mounting a flapper t valve in the exhaust outlet for pivoting movement about one edge of the flapper valve to cause the swinging movement of the flapper valve about the pivot to be dependent upon the exhaust gas flow and including connecting the flapper valve to a control valve in the recycle conduit in a way that permits more movement of the flapper valve on wide open throttle at high speeds than wide open throttle at low speeds but still maintains the control valve in said second position;

29. The invention defined in claim 26 including mounting the recycle valve in the exhaust gas recycle conduit for longitudinal movement with respect to a the recycle valve in said second position. 

1. An exhaust gas recirculation system for an internal combustion engine of a kind having an exhaust outlet, a fuel-air intake and an exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said system comprising, valve means in the recycle conduit for regulating the amount of flow of said recycled exhaust gases through the recycle conduit, and control means responsive to the exhaust gas flow in said exhaust outlet for positioning said valve means , said control means including a valve in the exhaust outlet mounted for movement in response to changes in exhaust gas flow and operatively connected to said valve means in the recycle conduit for controlling the exhaust gas recirculation through many changes in engine operating conditions.
 2. The invention defined in claim 1 wherein the valve means are contoured to restrict the flow of exhaust gas through the conduit to a first minimum in a first position of the valve means, to restrict the flow to a second minimum in a second position of the valve means, and to permit greater flow than said minimums in all positions of the valve meaNs between said first and second positions.
 3. The invention defined in claim 2 wherein the valve means include a fixed valve seat and a movable valve element.
 4. The invention defined in claim 3 wherein the valve means include an annular seat and the valve element has an elongated body movable in the annular seat and has a flange which engages the annular seat in the first position.
 5. The invention defined in claim 4 wherein the body is tapered and has a small diameter immediately adjacent the flange and a large diameter at an end of the body away from the shoulder.
 6. The invention defined in claim 5 wherein the taper is contoured to maintain a desired relationship of exhaust gas recirculation flow to movement of said control means.
 7. The invention defined in claim 2 wherein the control means are effective to position the valve means in the first position at engine idle.
 8. The invention defined in claim 2 wherein the control means are effective to position the valve means in the second position at wide open throttle.
 9. The invention defined in claim 2 wherein the control means are effective to position the valve means in positions between the first and second positions at conditions of engine operation between idle and wide open throttle.
 10. The invention defined in claim 1 wherein the valve includes a portion large enough to extend across substantially the entire cross-sectional area of the flow area through the exhaust outlet and including start-up means for preventing the valve from moving to a position in which the valve completely blocks flow through the exhaust outlet during engine start-up.
 11. An exhaust gas recirculation system for an internal combustion engine of a kind having an exhaust outlet, a fuel-air intake and an exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said system comprising, valve means in the recycle conduit for regulating the the amount of flow of said recycled exhaust gases through the recycle conduit, and control means responsive to the exhaust gas flow in said exhaust outlet for positioning said valve means and wherein the control means include a flapper valve which extends across at least a substantial part of the exhaust outlet so as to be subjected on one face to a force which is dependent upon the exhaust gas flow and which force is in general relation to engine speed and power between idle and wide open throttle, pivot means supporting the flapper valve for pivoting movement about a pivot substantially away from the center towards one edge of the flapper valve, and connecting means for transmitting pivoting movement of the flapper valve to said valve means in the recycle conduit.
 12. The invention defined in claim 11 wherein the connecting means include an articulated connection.
 13. The invention defined in claim 12 wherein the connecting means include biasing means for moving the valve means to a first position in which the valve means greatly restrict or block all flow through the recycle conduit at exhaust flows through said exhaust outlet corresponding to idle operation of the engine.
 14. The invention defined in claim 13 wherein the valve means are contoured to greatly restrict or block all flow through the recycle conduit in a second position of the valve means at exhaust gas flows corresponding to engine operation at wide open throttle.
 15. The invention defined in claim 11 wherein the pivot means include a flexible hinge member.
 16. The invention defined in claim 11 wherein the pivot means include a pivot pin and bushing.
 17. The invention defined in claim 16 including flexible means in the connecting means for permitting the flapper valve to swing further about the pivot means at exhaust gas flows at wide open throttle at high speeds than at wide open throttle at low speeds without changing the valve means from said second, flow blocking position.
 18. The invention defined In claim 11 wherein the flapper valve is large enough to extend across substantially the entire cross-sectional area of the exhaust outlet and including start-up means for preventing the flapper valve from swinging about the pivot to a position in which the flapper valve completely blocks flow through the exhaust outlet during engine start-up.
 19. The invention defined in claim 18 wherein the start-up means include an adjustable stop.
 20. The invention defined in claim 18 wherein the start-up means include means actuated in response to starting of the engine.
 21. The invention defined in claim 11 wherein the connecting means include a roller which engages one surface of the flapper valve and which is movable along said surface with changes of angular position of the flapper valve about the pivot means.
 22. The invention defined in claim 2 wherein the engine includes a power valve for enriching the fuel-air ratio in the intake for acceleration at or near wide open throttle and including coordinating means for insuring that the valve means are in said second recycle flow blocking or restricting position during enrichment of the fuel-air ratio by said power valve.
 23. The invention defined in claim 22 including delay means for delaying the opening of the power valve for a preselected period of time after the throttle is opened to or near wide open position.
 24. An exhaust gas recirculation system for an internal combustion engine of a kind having an exhaust outlet, a fuel-air intake and an exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said system comprising, valve means in the recycle conduit for regulating the amount of flow of said recycled exhaust gases through the recycle conduit, and control means responsive to the exhaust gas flow in said exhaust outlet for positioning said valve means and wherein the valve means are contoured to restrict the flow of exhaust gas through the conduit to a first minimum in a first position of the valve means, to restrict the flow to a second minimum in a second position of the valve means, and to permit greater flow than said minimums in all positions of the valve means between said first and second positions and wherein the engine includes a power valve for enriching the fuel-air ratio in the intake for acceleration at or near wide open throttle and including coordinating means for insuring that the valve means are in said second recycle flow blocking or restricting position during enrichment of the fuel-air ratio by said power valve and including delay means for delaying the opening of the power valve for a preselected period of time after the throttle is opened to or near wide open position and including stop means movable to a first position in which the stop means prevent movement of the recycle valve means to the flow blocking or restricting position at or near wide open throttle.
 25. The invention defined in claim 24 wherein the coordinating means move the stop means to a second position simultaneous with opening of the power valve to permit the valve means in the recycle conduit to move to the flow blocking or restricting position simultaneous with the opening of the power valve.
 26. A method of controlling exhaust gas circulation through an exhaust gas recycle conduit in an internal combustion engine of the kind having an exhaust outlet, a fuel-air intake and said exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said method comprising, restricting exhaust gas recirculation in said recycle conduit to a first minimum at idle, restricting exhaust gas recirculation in said recycle conduit to a second minimum at wide open throttle and controlling the amount of exhaust gas recirculation between idle and wide open throttle in response to exhaust gas flow in the exhaust outlet and including mounting a control valve in the exhAust outlet for movement in response to changes in exhaust gas flow, mounting a recycle valve in the recycle conduit and operatively connecting the control valve to the recycle valve.
 27. The invention defined in claim 26 including mounting a flapper valve in the exhaust outlet for pivoting movement about one edge of the flapper valve to cause the swinging movement of the flapper valve about the pivot to be dependent upon the exhaust gas flow.
 28. A method of controlling exhaust gas circulation through an exhaust gas recycle conduit in an internal combustion engine of the kind having an exhaust outlet, a fuel-air intake and said exhaust gas recycle conduit for recycling a part of the exhaust gases from the exhaust outlet back to the fuel-air intake, said method comprising, restricting exhaust gas recirculation in said recycle conduit to a first minimum at idle, restricting exhaust gas recirculation in said recycle conduit to a second minimum at wide open throttle and controlling the amount of exhaust gas recirculation between idle and wide open throttle in response to exhaust gas flow in the exhaust outlet and including mounting a flapper valve in the exhaust outlet for pivoting movement about one edge of the flapper valve to cause the swinging movement of the flapper valve about the pivot to be dependent upon the exhaust gas flow and including connecting the flapper valve to a control valve in the recycle conduit in a way that permits more movement of the flapper valve on wide open throttle at high speeds than wide open throttle at low speeds but still maintains the control valve in said second position.
 29. The invention defined in claim 26 including mounting the recycle valve in the exhaust gas recycle conduit for longitudinal movement with respect to a valve seat to cause the movement of the recycle valve to be dependent upon the exhaust gas flow.
 30. The invention defined in claim 29 including connecting the recycle valve to the control valve in the exhaust conduit in a way that permits more movement of the control valve on wide open throttle at high speeds than wide open throttle at low speeds but still remains the recycle valve in said second position. 